it seems like when it works it gets the credit..."best thing that we ever did" ..."we are so so much closer now..... and I'm so much happier now and partner is happy that I'm happy ..its just a big ball of loving happiness ... its a win win win ".

I wouldn't necessarily give poly the credit. As I see it, the statements above are likely due to the fact that the couple are BOTH putting in extra time and effort to make their relationship work. They are paying attention to each others needs and sensitivities, not just to get something in return, but because the relationship is worth it. The couple will talk/communicate more, make the effort to schedule more time together, make the effort to calm each others insecurities, etc.

Just as poly can be the "straw that breaks" a marriage, it can also be the catalyst for each partner to "make the extra effort".